Technical Field
Embodiments of the present disclosure generally relate to an image forming apparatus and an image forming method.
Description of the Related Art
A known image forming apparatus has a plurality of sub modules such as a photoconductor drum, a charging device, an exposure device, a developing device, a transfer device. In the image forming apparatus, the charging device uniformly charges the rotating photoconductor drum. Then, the exposure device exposes the surface of the charged photoconductor drum to form an electrostatic latent image on the photoconductor drum. The developing device develops the electrostatic latent image formed on the photoconductor drum into a visible toner image, and the transfer device transfers the obtained toner image onto a recording medium.
To decrease image density fluctuation of the image, the image forming apparatus forms a predetermined toner image pattern at a predetermined timing, detects an image density of the formed toner image pattern, and adjusts operating parameters of the submodules of the image forming apparatus based on the detected image density. Examples of the operating parameters include a charging bias in the charging device, a luminous energy of a light beam irradiated from the exposure device, a developing bias in the developing device, a toner supply amount, and an output of the transfer device.
In the image forming apparatus, tolerances of the photoconductive layer formed on the photoconductor drum or the photoconductor drum itself are such that, even when the above-described operating parameters are set properly, an image density fluctuation sometimes occurs in a rotation direction of the photoconductor drum, that is, in a sub-scanning direction. In addition to the photoconductor drum, a predetermined dimensional error is also allowed for a charging roll provided in the charging device, a developing sleeve provided in the developing device, a transfer roll provided in the transfer device, and the like, respectively. Therefore, these submodules may also cause the image density fluctuation in the sub-scanning direction when an image is formed.